EŠect of Repetitive Biphasic Muscle Electrostimulation Training on Vertical Jump Performances in Female Volleyball Players

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1 Brief Paper : Physiology Int. J. Sport Health Sci. EŠect of Repetitive Biphasic Muscle Electrostimulation Training on Vertical Jump Performances in Female Volleyball Players Tanguy Marqueste, Folly Messan, Francois Hug, J áer âome Laurin, Erick Dousset, Laurent Grelot and Patrick Decherchi* Institut des Sciences du Mouvement: Etienne-Jules MAREY (UMR CNRS 6233) Universitáe de la M áediterranáee (Aix-Marseille II) Parc Scientiˆque et Technologique de Luminy Facultáe des Sciences du Sport de Marseille Case Postale , avenue de Luminy Marseille Cedex 09, France. patrick.decherchi@univmed.fr [Received June 27, 2008; Accepted March 10, 2010; Published online April 7, 2010] The aim of this study is to describe the ešects of transcutaneous muscular electrical stimulation on vertical jump performance (jumping height). Electromyostimulation (30 min/day, 10 sessions during 4 weeks) was applied, using a symmetric and biphasic rectangular pulses, with ramp modulation of both pulse duration and stimulation frequency. Ten healthy young women received this electrical stimulation program of the two thigh muscles (Vastus Lateralis or Biceps Femoris) and ˆve unstimulated women were in a control group. EŠects of the functional electrical stimulation were evaluated before, during the stimulating protocol, then a 4-week follow-up was performed after the end of exercises and stimulations protocols. Two dišerent vertical jumps were carried out (squat and counter movement jumps). Performances were increased in all electrostimulated groups from the ˆrst week. These gains were still observed 4 weeks after the end of the protocol when the Vastus Lateralis muscles were electrostimulated. These results suggest that chronic electrical stimulation induces durable changes on the motor unit recruitment and performance when appropriate muscles were stimulated, and stimulation of thigh muscles weakly involved in jump is followed by a temporarily increase in performance that decreases immediately after the end of electrostimulation, maybe due to placebo ešect. Keywords: Squat Jump, Counter Movement Jump, Functional Electrostimulation, Placebo 1. Introduction Electromyostimulation (EMS) also called functional electrical stimulation (FES) is mainly used in rehabilitation programs when the neuromuscular function has been injured, and also as a sport training method. It has been used in swimming, basketball, volleyball or cycling practices involving Latissimus Dorsi, Quadriceps, Vastus Lateralis (VL) or Triceps Surae muscles respectively. EMS results in a reversal of recruitment order of the motor units with a preferential activation of the largest motor units ˆrst (Enoka, 1988) and a possible preferential adaptation of the type II motor units (Ma uletti et al., 2000). Previously, Ma uletti et al. (Ma uletti et al., 2000), using EMS combined with plyometric training reported an improvement of vertical jump ability in male volleyball players and a rapid increase of the knee extensors and plantar exors maximal strength. These adaptations were then followed by an improvement of the speciˆc jumping ability, likely to ašect performance on the short term. Then, complementary of EMS sessions with a speciˆc work out (i.e. plyometric) allowed to obtain beneˆcial ešects. In our previous study (Marqueste et al., 2003), we observed an increase in strength after an EMS training of Rectus Femoris (RF) and Flexor Digitorum (FD) muscles associated with a lack of M- wave alterations, suggesting that the EMG parameters changes (root mean square and median frequency) did not result from eventual muscle 50 International Journal of Sport and Health Science Vol.8, 50-55, 2010

2 EMS and Vertical Jump Performances membrane excitability alterations, but more probably from some changes in the motor units recruitment. The purpose of this study was to determine if a 4- week electromyostimulation training with a speciˆc current, previously described to have beneˆcial ešects on animal and Human muscles (Marqueste et al., 2002, Marqueste et al., 2003), could increase jump performance during the pre-season training in volleyball athletes. 2. Materials and Methods 2.1. Subjects Fifteen healthy trained women (age: 20.6±1.3 years, height: 1.68±0.05 m, weight: 62.0±5.0 kg) participated at this study. They were randomly assigned in three groups: the control group (n=5, without EMS), the sham (placebo) group (n=5, EMS was applied on the Biceps Femoris muscles) andtheemsgroup(n=5,emswasappliedonthe Vastus lateralis). These aforementioned groups were designated as Control, BF and VL groups. It had been previously shown that the VL muscle was in half part involved (50 z) in the jumping performance (Hubley and Wells. 1983). Thus, the quadriceps muscles are necessary during squat jump (SJ) and counter movement jump (CMJ) contrary to the non-implication of Biceps Femoris muscles. Biceps Femoris (BF) muscle has two heads: the long head arises from the lower and inner part of the ischium, and from the lower part of the sacrotuberous ligament. The short head arising between the adductor magnus and vastus lateralis, is really small (about 5 cm) and located just above at the popliteal area (Netter 2006). Due to its size and position, this latter is not stimulated during our EMS protocol. However both heads of the BF perform knee exion. Since the long head originates in the pelvis it is also involved in hip extension, but the long head is a weaker knee exor when the hip is extended (because of activation insu ciency). For the same reason the long head is a weaker hip extender when the knee is exed. During squat jump (SJ) or counter movement jump (CMJ) the subjects were asked to maintain a vertical position of the trunk (i.e. extension of the hip) and to induce a knee exion during CMJ or to maintain this position before SJ. Therefore we choose the BF muscle on purpose in order to investigate a sham-placebo ešect of EMS on muscle weakly involved our studied movement. All subjects were involved in volleyball training program at the university during 4 hours per week and were in pre-season training at the time of the protocol. The possible risk of harm or pain due the protocol were previously explain in a clear document in accordance with the local ethical commission of the Universitáe de la Máediterranáee (Aix-Marseille II) who gave its permission Electromyostimulation Muscles were stimulated during 10 sessions of 30 min distributed on a 4-week period. As we previously described (Marqueste et al., 2002), the stimulation pattern consisted in a biphasic and symmetric (the wave having consecutive and symmetrical positive and negative peaks) pulse current (around 100 V, i.e. daily adjusted by each subjects in order to have maximal but not painful contraction) with a ramp modulation of frequency (means gradual and linear increase of frequency from 4 to 75 Hz and decrease to 4 Hz) and pulse duration ( ms). Each stimulation pattern lasted for 11-s and it was repeated twice a minute with a rest of 19-s between each stimulation. Biceps Femoris or Vastus Lateralis muscles from the both legs were stimulated. EMS was delivered through a clinical stimulator (Multiprocess 16+, Physitech}, Electronique Medicale Marseille, France) used for electrophysiotherapy and kinesitherapy. The stimulating electrodes were placed on the motor point of each muscle deˆned as the point on the surface of the skin over the muscle belly at where the smallest amount of current is required to produce muscle contraction. The surface of the electrodes were 3 5 cm with 5 cm inter-electrode distance (center to center); the anode being over the muscle endplate estimated at the middle of the muscle belly and the cathode above, with and impedance value adjusted and measure between 0.5 and 1 MQ by cleaning skin surface with alcohol and ether. Concentric contractions were elicited by EMS Vertical jumps Subjects were tested before (week 0), at the beginning and at the end of each session during the International Journal of Sport and Health Science Vol.8, 50-55,

3 Marqueste, T., Messan, F., Hug, F., Laurin, J., Dousset, E., Grelot, L. and Decherchi, P. moment of the touch down. The height (h) of jump was then calculated by using the ight time (t) of the respective jumps (h=1/8.g.t 2 ). Jumpers were asked to jump as high as they could. In order to avoid dišerence of limb posture that could lead to the dišerence of ight time, we verify with a video recording (Numerical camcorder Canon TM, MV 830i, Unterschleissheim, Germany) linked to a walking track apparatus (Simi-Motion} software, 50-Hz acquisition frequency, Unterschleissheim, Germany)thattheposturesofthelowerlimbwere identical between at the take-oš and at the landing and between pre-training and post-training. Three trials of each SJ and CMJ were measured, with a 3- min rest between jumps. The best performance was retained and included in subsequent analysis Statistical analysis Figure 1 Squat (SJ) and Counter Movement (CMJ) Jump. A. The two steps of the SJ: starting from a static semisquatting position maintained 1-s without movement, then jump in pure concentric contraction of lower limb muscles. B. The three steps of the CMJ: starting from a stand up position, squatting down and then extension in one continuous movement. Extensor muscles involved are ˆrst stretched and then shortened to accelerate the body or limb. This action of the muscles is called a stretch shortening. We can note that during the jump, the hands were kept on the hips to minimize the contribution of the upper limbs. program (week +4) and once again 4 weeks after the last training session (week +8). A standardized warm-up, lasting 5 min, was carried out before each testing session and consisted of several contractions of the lower limb muscles (i.e. squat, leg extension and jump). Subjects performed the following vertical jumps with their hands kept on the hips to minimize the contribution of the upper limbs: squat jump starting from a static semi squatting position (909of exion) maintained for one second without any preliminary movement (SJ) (Figure 1A); counter movement jump starting from a standing position, squatting down and then extension in one continuous movement (CMJ) (Figure 1B). An electronic timer was connected to an optical acquisition system for measuring the ight time (Optojump}, Microgate,Bolzano,Italy).Thetime onset was triggered by the unloading of the jumpers' feet from the ground and was stopped at the Data processing was performed by using a software program (SigmaStat}, Jandel, Chicago, Illinois, USA) on the raw values. Data are presented as mean±sem. An analysis of variance on repeated measures was used to assess the ešect of the training program at week 0, over the 10 sessions during the training program, then at week 8. Student-Newman- Keuls post-hoc tests were used to analyze the dišerences. A dišerence was accepted as statistically signiˆcant when pº Results After4weeksofstimulation,SJ(BF:23.5±2.4 cm and VL: 30.3±3.9 cm) and CMJ (BF: 28.9±2.2 cm and VL: 34.6±4.2 cm) heights are signiˆcantly increased compared to pre-training values [SJ (BF: 20.2±2.7 cm and VL: 23.8±3.3 cm), CMJ (BF: 22.2±2.9 cm and VL: 28.15±3.5 cm)]. For the SJ, performance increases were +16.4±2.4z (BF) and +26.9±3.8z (VL) whereas for the CMJ, increases were +30.2±2.1z (BF) and +23±4.2z (VL). Except for the control group (Figure 2A), SJ ability was signiˆcantly increased from the ˆrst week in the VL group (+11.1±4.8z) and surprisingly in the placebo BF group (+16.4±2.9z). These signiˆcant gains in vertical jump height were maintained during the 4 weeks of the volleyball training plus EMS; the VL group conserving signiˆcant gain (+26.5±4.3z) 4weeksafterthe endoftheemstraining(figure 3A). 52 International Journal of Sport and Health Science Vol.8, 50-55, 2010

4 EMS and Vertical Jump Performances Figure 2 Evolution of the jumping height values during a 4 weeks training period (10 sesions) with an electromyostimulation protocol. Electrical stimulation was applied to the Biceps Femoris (BF) or Vastus Lateralis (VL) muscles. Control group received no stimulation. A. Squat Jump (SJ). B. Counter Movement Jump (CMJ). Asterisks indicate a signiˆcant dišerence (pº0.05) compared to the height values recorded in pre-test (week 0) session. Heights measured during the CMJ presented a signiˆcant increase from the ˆrst week in the both electrostimulated (VL: +12.3±2.3z and BF: ±4.8z) and control (+6.9±3.8z) groups (Figure 2B). The ešect persisted 4 weeks after the endoftheemstrainingprogramonlyinthevl group (+21.4z) (Figure 3B). 4. Discussion The present study indicated that EMS training before a volleyball training season improves the performance in the vertical jump. The main ˆndings of this study demonstrated that a 4-week EMS program during the volleyball pre-season training signiˆcantly increased the height of dišerent vertical jumps as compared to the sole pre-season training. More surprisingly, the present study shows an increase in the jumping performance even when Biceps Femoris muscle, poorly involved in these jumps, was stimulated. However, gains observed in Figure 3 Comparison of the jumping height values between the pre-test (week 0), the post-test (week +4) and the delayedtest (week +8, i.e. 4 weeks after the end of the electromyostimulation protocol). Electrical stimulation was applied to the Biceps Femoris (BF) or Vastus Lateralis (VL) muscles. Control group received no stimulation. A. Squat Jump (SJ). B. Counter Movement Jump (CMJ). Asterisks indicate a signiˆcant dišerence (pº0.05) compared to the height values recorded in pre-test (week 0) session. vertical jump performance were lost as soon as the EMS session was stopped. Thus, it seems that EMS could act on motivational pathways, i.e., the placebo ešect could be responsible in this temporary performance increase. EMS (Ma uletti et al., 2000), weight or plyometric training alone or combined (weight/ plyometric or EMS/plyometric)(Ma uletti et al., 2002) increased signiˆcantly vertical jump heights. Ma uletti et al. (Ma uletti et al., 2000) reported in basketball player a signiˆcant increase in SJ performance after a 4-week EMS training program; the CMJ performance remained unchanged. In our study, we observed also an increase in CMJ performance during the 4-week EMS period, remaining high one month after the end of EMS. This discrepancy between our results and those of Ma uletti et al. (Ma uletti et al., 2000) could be explain by the fact that our subjects were 1) volleyball players and 2) involved in a pre-season International Journal of Sport and Health Science Vol.8, 50-55,

5 Marqueste, T., Messan, F., Hug, F., Laurin, J., Dousset, E., Grelot, L. and Decherchi, P. training program. During CMJ, the muscles are stretched while they were actived. As a result of this muscular lengthening, potential energy is stored in the elastic component and then released during the subsequent shortening. Ma uletti et al. (Ma uletti et al., 2000) suggested that improvements in strength of muscles involved in complex movements using elastic energy, such as CMJ, require a longer period of speciˆc training before beneˆcial ešects are observed in jumping performance and that EMS training is not speciˆc to develop elastic behaviour of skeletal muscle. However, these authors also reported an increase in jumping height during CMJ when they associated EMS with plyometric jumps training. In our study, the immediate increase in jumping performance during CMJ could be due to a speciˆc pre-season training program used by our volleyball players or by apprenticeship of a new speciˆc and unusual jump from our subjects. This can be conˆrmed by the rapid increase in jump performance during CMJ in the control unstimulated group and the reduced dišerence in height observed with the two EMS groups (Figure 2B). Several authors reported that the percentage of fast twitch ˆbers in a muscle was an important factor for force development during maximal static ešorts (Thorstensson et al., 1976) suggesting that EMS training increased the activation and thus the contribution of the fast twitch muscle ˆbers (Enoka, 2002), only able to develop the highest force during maximal voluntary contraction. Except in paralysed or partially paralysed subjects, EMS opposes the physiological recruitment order of motor units found during a voluntary contraction, in which, according to the Henneman' size principle; the smallest motoneurons (supplying the type I muscle ˆbers) are ˆrst activated (Enoka, 2002). During such EMS condition, recruitment order depends on 1) the characteristics of the current used (Thorstensson et al., 1976), 2) the distance between the stimulating electrode and the peripheral axon, i.e., the larger axon of the largest diameter motor units are often superˆcially located in the muscle or the axon collaterals, i.e., the axon excitation threshold being inversely proportional to its diameter (Enoka, 2002) 3) the activation of the cutaneous and proprioceptive ašerents (''feedback ešects''). The marked attenuation of the changes in RMS (Root Mean Square) during fatiguing ešorts immediately after the EMS training (Marqueste et al., 2003), and their persistence 4 weeks after the end of the training, could be interpreted as a long-term facilitation occurring in the central nervous system elicited by some changes in the ašerent pathways arising from the stimulated muscles, and 4) the changes induced by the EMS (proportions, metabolic and contractile properties of the muscle ˆbers). During a maintained voluntary static contraction the force failure is associated with a MF (Median Frequency) decline and a RMS increase, indicating a neuromuscular fatigue. After EMS training (Marqueste et al., 2003), the analysis of 60z MVC trials during the post-tests showed a median frequency decline and also a non signiˆcant RMS increase. The attenuation of EMG signs of neuromuscular fatigue was associated with an increased in MVC. Montes-Molina et al. (Montes Molina et al., 1997) suggested that electrical stimulation produces immediate changes on the motor unit: increasing the recruitment number of ˆbers, namely a selective recruitment of type II ˆbres, and also their action potential velocity. After a 10-day EMS period, they reported a signiˆcant changes in the MF and RMS, measured during exercise. Due to the absence of changes in M-wave duration in our previous protocol using the same stimulating current, this explanation could be discarded. Indeed, as previously reported, the duration of M-wave should be then reduced, and the intramuscular conduction velocity should increase. We also suggested the EMS-induced changes in the EMG response to sustained static voluntary ešort was due to the occurrence of an enhanced aerobic pathway with EMS that should reduce the intramuscular release of metabolites, including the lactate. This should reduce the activation of the free ending chemosensory muscle ašerent ˆbers (the group III and IV ašerents ˆbers) which are supposed to trigger the EMG changes during fatiguing ešorts, namely the power spectrum shift towards the lowest frequencies. The last explanation would be that EMS could have elicited some speciˆc changes in the excitability of this muscle ašerents endings, namely in their capability to detect the metabolic variations preceding fatigue. EMS training is responsible for a durable neuromuscular functional adaptation which persisted for several weeks after the end of the 54 International Journal of Sport and Health Science Vol.8, 50-55, 2010

6 EMS and Vertical Jump Performances training. A preferential recruitment of the fast twitch muscle ˆbers during EMS could be responsible of these supposed changes in the central neural drive but could also involve some changes in the chemosensitive ašerent muscle pathways. Therefore, EMS training remains a method to enhance the performance and could be used during the pre-season training to enhance vertical jump performance without interfering with training; player's abilities being maintained at a high level after the end of the EMS program. Acknowledgements We are grateful to Fráedáeric GOUNARD (Physitech}, Electronique M áedicale) and, Francis BERTHELIN, Ferdinand TAGLIARINI (Facultáe de Máedecine Nord, Marseille) for technical assistance and ALARME (Association Libre d'aide àa la Recherche sur la Moelle Epiniere), and DGA-DSP (Dáeláegation Generale pour l'armement, n ) for grants. References Enoka, R. M. (1988). Muscle strength and its development. New perspectives. Sports Med. 6: Enoka, R. M. (2002). Activation order of motor axons in electrically evoked contractions. Muscle Nerve. 25: Hubley, C. L. & Wells, R. P. (1983). A work-energy approach to determine individual joint contributions to vertical jump performance. Eur J Appl Physiol Occup Physiol. 50: Ma uletti, N. A., Cometti, G., Amiridis, I. G., Martin, A., Pousson, M., & Chatard, J. C. (2000). The ešects of electromyostimulation training and basketball practice on muscle strength and jumping ability. Int J Sports Med. 21: Ma uletti,n.a.,dugnani,s.,folz,m.,dipierno,e.,& Mauro, F. (2002). EŠect of combined electrostimulation and plyometric training on vertical jump height. Med Sci Sports Exerc. 34: Marqueste, T., Decherchi, P., Dousset, E., Berthelin, F., & Jammes, Y. (2002). EŠect of muscle electrostimulation on ašerent activities from tibialis anterior muscle after nerve repair by self-anastomosis. Neuroscience. 113: Marqueste, T., Hug, F., Decherchi, P., & Jammes, Y. (2003). Changes in neuromuscular function after training by functional electrical stimulation. Muscle Nerve. 28: Montes Molina, R., Tabernero Galan, A., & Martin Garcia, M. S. (1997). Spectral electromyographic changes during a muscular strengthening training based on electrical stimulation. Electromyogr Clin Neurophysiol. 37: Netter, F. H. (2006). Atlas of Human Anatomy, 4th Edition. Saunders. Thorstensson, A., Grimby, G., & Karlsson, J. (1976). Forcevelocity relations and ˆber composition in human knee extensor muscles. J Appl Physiol. 40: Name: Patrick Decherchi A liation: University of the Mediterranean-Aix- Marseille II (France) Address: UMR CNRS 6233-Institute of Movement Sciences Brief Biographical History: 39 international publications Main Works: Anatomical and functional plasticity of the central and peripheral nervous system Membership in Learned Societies: Patrick DECHERCHI is Assistant Professor of Physiology and director of studies of the master degree of ``Sciences and Technologies of Human Movement'' (SMTH) at the Faculty of Sport and Sciences in the University of the Mediterranean (Aix- Marseille II, France) since He is the head of the team ``Plasticity of Neural and Muscular Systems'' (PSNM) in the Institute of Movement Sciences (UMR CNRS 6233, University of the Mediterranean- He obtained his Ph.D. in ``Neuroscience'' (Neurobiology/Neurophysiology) in Immediately after his Ph.D., he worked for one year for the French Military Ministry as Engineer. From 1997 to 1999, he was Research Associate at the National Institute for Medical Research (Division of Neurobiology, UK) in London. His research topics concern the anatomical and functional plasticity of the central and peripheral nervous system. International Journal of Sport and Health Science Vol.8, 50-55,

Electrostimulation for Sport Training

Electrostimulation for Sport Training abstracts collected by Globus Sport and Health Technologies The effects of electromyostimulation training and basketball practice on muscle strength and jumping ability;...